Spark-plug



D. L. ARNOLD.

SPARK PLUG. APPLICATION FILED JUNE 25. I919.

Patented May 3,1921.

UNITED STATES PATENT OFFICE.-

DOUGLASS L. ARNOLD, OF CHICAGO, ILLINOIS, ASSIGNOR TO INTERNATIONAL HARVESTER COMPANY, ACORPORATION OF NEW JERSEY.

' SPARK-PLUG.

Application filed June 25,

T 0 all whom it may concern Be it known thatoI, DOUGLASS L. ARNOLD, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Spark-Plugs, of which the following is a full, clear, and exact specification.

This invention relates to spark plugs,

An object of the invention is to provide a spark plug which will be gas tight, and which at the same time can be readily assembled and disassembled for inspection and cleaning.

Another object is to provide a spark plug which will always have the same spark gap, no matter how carelessly it is assembled.

These and other objects, as will hereinafter appear in the specification, consist of a spark plug having an insulator, the upper portion of which is tapered, a nut in alinement with said insulator, shoulders on the nut and insulator forming substantiallya continuous surface, a hollow casing having an internal shoulder and a gasket between said shoulder and the shoulders on the nut'and insulator.

Reference is now had to the accompanying sheet of drawings in which Figure 1 is a longitudinal section through my spark plug; and Fig. 2 is an enlarged sectional'view of that portion of my spark plug, showing the end of the nut inclined at an angle forming a continuous surface with the "inclined shoulder of the insulator,"as hereinafter-described andclaimed.

This spark plug has a metallic casing 10 which is threaded 'inthe usual way for screwing. into a cylinder head, while a hexagonalportion 11 is providedat the upper end to which a wrench may be applied. This casing has a longitudinal bore whichis threaded. at the upper end and. has a shoulder 12, the pur ose of which will be hereinafter-explaine Into this casing is adapted to be screwed at its upperend a nut 13 which is internally tapered, narrowingtoward the upper end. Into this is fitted a ta ered insulator 14 which I prefer to make 0 mica,'having a shoulder 15 which is preferably placed at an angle to the longitudinal axis of the insulator, and which preferably lies insubstantially the same surface as the lower end 13 of the nut 13. The surface of the shoulder 12- in the inte-' Specification of Letters Patent.

Patented May 3, 1921. 1919. Serial No. 306,664.

rior of the casing is also preferably placed at substantially the same angle as that of the shoulders 13 and 15. A gasket 16 which is preferably made of metal is placed between these shoulders, and acts as a seal.

In the center of the insulator 14 is .placed a rod 17 which carries at its lower end a head 18 and a spark terminal 19. The upper end of this rod is threaded and carries the usual nut 20 and thumb nut 21. At the lower edge of casing 10 Ihave placed-a spark pin 22 which I have preferably inserted at an angle. It will be noted that by 'my arrangement of the shoulders with respect to the gasket 16, that as the nut 13is screwed into the casing 10, the shoulder formed by the lower edge 13 of the nut 13 will very firmly and uniformly grip the outer edge of the gasket 16 forming a very tight joint through which gas will not be able to pass. At the same time, the inner edge of this gasket presses against the shoulder 15 of the insulator 14, thereby maintaining the insulator tight in the nut 13. By reammg the inside of the nut 13 and by turning the tapered portion of the msulator 14 to the'same angle and by forcing the nut down upon the insulator I am able to get a joint between these two which 1s perfectlygas tight. This careful fitting also insures that the spark terminal 19 willalways be'perfectly centered and hence the spark gap between the terminals 19 and 22 will always remain substantially constant. While I have preferably shown and described a spark plug having an insulator of mica, I wish it to be understood that I am not limited to mica, but that the insulator may be made of any suitable insulating ma terl'al.

While I have in the above specification described but a single embodiment of'my invention,.it is to be understood that it is capable of many modifications. Changes, therefore, in the construction and arrangement d parts may be made which do not shoulders on the nut and insulator forming substantially a continuous surface, a hollow casing havlng an inclined internal shoulder,

and a gasket between said shoulder and the I vshoulders on the nut and insulator.

3. In a spark plug, a casing having an internal tapered shoulder, a gasket engag- 'an inclined surface forming a continuationingsaid" shoulder, an insulator having its upper 1 portion tapered and an inclined shoulder at the lower end oflthe tapered portion, a'nut having a tapered bore adapted to fit the tapered insulator and having insulator, the ,upper portion of which is tapered, a nut in 4 alinement with said insulator, inclined of the inclined surface on the insulator, the

inclined portion of the nut and insulator cooperating with the gasket and inclined shoulder on the casing to form a gas-tight joint and to maintain the insulator centrally in the casing.

4. In a spark plug, a casing having an internal tapered shoulder, an insulator disposed oentrally in the casing, a nut fitted around said insulator, said insulator and nuthaving inclined shoulder portions forming a substantially continuous surface, and a gasket fitted between the shoulder on the casing and the inclined shoulder portion of the nut and insulator, whereby a gas-tight joint is made.

In testimony whereof I aflix my signature.

DOUGLASS L. ARNOLD. 

